An old Archie story, “Mop Up,” reprinted in Jughead and Archie Comics (Annual) Digest 27 (October 2017), proves there was a library in Riverdale High. Well, it proves that there was a library at least once, but the way things change in the Archie universe, we can’t be sure if it was always there.
Everyone is in a rush to return their overdue books to the high school’s library, because if they’re not back by 3 pm, Principal Weatherbee will punish them.
Svenson is mopping the floors, and first we see Archie sliding on the wet floor, then later Jughead. The gag is that Principal Weatherbee also slips on the floor and is knocked out for so long that everyone has time to return their books, so there is no punishment. Of course head injuries and concussions are not amusing in real life.
We never actually see the library in this story, so I have no more clues about what it looks like or who the librarian is.